What is the difference between MP4 and WebM?
MP4 is the most widely supported video format. It usually holds H.264 video and AAC audio, and phones, TVs and editors open it. WebM is an open format that Google introduced in 2010 for the web. Chrome, Firefox and Edge play it natively.
Here, the MP4 export uses H.264 with AAC audio at 128 kb/s, while the WebM export uses VP8 video with Opus audio at 96 kb/s. WebM suits sites and web apps. MP4 suits devices and editing programs.
How to convert MP4 to WebM
- Drop your MP4 file on the page, or choose it from your computer.
- Open the Convert tab and check that WebM is the selected output.
- Press Start and wait for the progress bar to finish.
- Check the preview, then download your WebM.
Technical specs
| Output | WebM: video VP8, audio Opus 96 kb/s |
|---|---|
| Processing | In your browser (FFmpeg.wasm), 0 files uploaded |
| Large files | Up to about 1.6 GB with FFmpeg, then the browser engine in real time |
| Output formats | 14 formats (MP4, WebM, MKV, MOV, AVI and more, plus GIF, MP3, WAV) |
| Price | Free, no account, no watermark added |
When should you convert MP4 to WebM?
Web developers often use WebM for background videos, animated banners and short demos on a page. Some web platforms, game engines and open source tools also ask for it. If the video will only play in a browser, WebM is a fine target.
Some Apple devices and older software may not open WebM, so keep your MP4 as well. A common approach is to offer both files on the page and let each browser pick the one it plays best.
Tips for a good conversion
Converting means encoding the video again, so a very small quality change is possible. Keep the MP4 until you have checked the WebM. If the file is too heavy for your page, trim it first, then use the Compress tab to reach a target size.
FFmpeg.wasm does the encoding. It downloads on your first export and your browser keeps it afterwards. If it cannot start, or if the file is larger than about 1.6 GB, the native engine takes over. It uses Canvas and MediaRecorder and works in real time, so the wait is close to the length of the video.
Questions
Is MP4 to WebM conversion free?
Yes. There is nothing to pay and no account to create. This site does not add a watermark. The conversion runs in your browser, so the file is never uploaded.
Which codecs does the WebM file use?
The WebM uses VP8 video with Opus audio at 96 kb/s. Both are open codecs, and Chrome, Firefox and Edge play this combination natively. The MP4 version uses H.264 with AAC audio at 128 kb/s.
Will the sound be kept?
Yes. The audio is converted together with the picture. If you want a silent file, open the Audio tab and switch on the option that removes the sound. For sound only, save an MP3 from the Audio tab.
Why is my WebM bigger or smaller than the MP4?
Each format uses different codecs and bitrates, so the size changes. Trim the clip or use the Compress tab if the WebM is too heavy for your page. Compare both files before you publish.
Can I convert other formats to WebM?
Yes. If your browser cannot play the source, such as AVI, FLV, WMV, MPEG, TS or OGV, FFmpeg still converts it, but without live preview. Choose WebM in the Convert tab and press Start.